Understanding the fruit sink.

This chapter deals with understanding the fruit sink by studying the floral development and structures; pollination, fertilization, fruit set and types; limitations of fruit growth; thinning effects on fruit growth, size and yield; spring temperature effects on fruit size; nut development and growth; and the condition of alternate bearing.

Mögliche künftige Trends der Lufttemperatur und des Blattaustriebs der Schwarzerle (Alnus glutinosa) in Deutschland

<p>Eine direkte Auswirkung des rezenten Klimawandels auf die Vegetation ist die Verfrühung phänologischer Stadien, besonders im Frühjahr (WALDAU & CHMIELEWSKI, 2018; CHMIELEWSKI et al., 2004; WOLFE et al., 2005). Diese Trends wurden weltweit beobachtet und sind hauptsächlich auf den Anstieg der Lufttemperatur zurückzuführen, was den engen Zusammenhang zwischen Pflanzenentwicklung und Temperatur belegt. Dieser stetige Temperaturanstieg wird sich in Zukunft fortsetzen und zu zeitlichen und räumlichen Verschiebungen in der Vegetationsentwicklung führen. Um diese Veränderungen abschätzen zu können, sind plausible phänologische Modelle erforderlich, wobei das Kältebedürfnis, das für die Überwindung der Dormanz erforderlich ist, hierbei eine der Schlüsselgrößen ist. <br />Ziel dieser Studie war es die zukünftigen Auswirkungen des Klimawandels auf die natürliche Vegetation in Deutschland abzuschätzen. In einer dreijährigen Studie (Winter 2015/16 – 2017/18) wurde der Zeitpunkt der Dormanzbrechung für verschiedene Baumarten experimentell in Klimakammerversuchen bestimmt. Im Rahmen dieses Vortrages sollen die Ergebnisse für die Schwarzerle (Alnus glutinosa) dargestellt werden. Nach der Ermittlung des für den Blattaustrieb der Schwarzerle notwendigen Kältereizes wurde ein Chilling/Forcing Modell parametrisiert und anschließend an den phänologischen Beobachtungdaten des Deutschen Wetterdienstes (1951-2015) validiert. Für die Abschätzung der künftigen klimatischen Entwicklung wurde ein Klimaensemble aus sieben verschieden Klimamodellrechnungen für zwei Klimaszenarien (RCP 2.6 & 8.5) verwendet. Für den Zeitraum 2010-2100 werden neben den zeitlichen Trends der Lufttemperatur und der Phänologie zusätzlich die regionalen Unterschiede in Deutschland (Nord-Ost/Nord-West/Süd-Ost/Süd-West) aufgezeigt.</p> <p> </p> <p>Literatur:</p> <p>CHMIELEWSKI, F. M., MÜLLER, A. & BRUNS, E. (2004): Climate changes and trends in phenology of fruit trees and field crops in Germany, 1961–2000. Agricultural and Forest Meteorology 121 (1), 69-DOI: https://doi.org/10.1016/S0168-1923(03)00161-8.</p> <p>WALDAU, T. & CHMIELEWSKI, F. M. (2018): Spatial and temporal changes of spring temperature, thermal growing season and spring phenology in Germany 1951–2015. Meteorol. Z. 27 (4), 335-342.DOI: https://doi.org/10.1127/metz/2018/0923.</p> <p>WOLFE, D. W., SCHWARTZ, M. D., LAKSO, A. N., OTSUKI, Y., POOL, R. M. & SHAULIS, N. J. (2005): Climate change and shifts in spring phenology of three horticultural woody perennials in northeastern USA. International Journal of Biometeorology 49 (5), 303-309. DOI: https://doi.org/10.1007/s00484-004-0248-9.</p>

Rapidly changing high-latitude seasonality: Implications for the 21st century carbon cycle in Alaska

Seasonal variations in high-latitude terrestrial carbon (C) fluxes are predominantly driven by air temperature and radiation. At present, high-latitude net C uptake is largest during the summer. Recent observations and modeling studies have demonstrated that ongoing and projected climate change will increase plant productivity, microbial respiration, and growing season lengths at high-latitudes, but impacts on high-latitude C cycle seasonality (and potential feedbacks to the climate system) remain uncertain. Here we use ecosys, a well-tested and process-rich mechanistic ecosystem model that we evaluate further in this study, to explore how climate warming under an RCP8.5 scenario will shift C cycle seasonality in Alaska throughout the 21st century. The model successfully reproduced recently reported large high-latitude C losses during the fall and winter and yet still predicts a high-latitude C sink, pointing to a resolution of the current conflict between process-model and observation-based estimates of high-latitude C balance. We find that warming will result in surprisingly large changes in net ecosystem exchange (NEE; defined as negative for uptake) seasonality, with spring net C uptake overtaking summer net C uptake by year 2100. This shift is driven by a factor of 3 relaxation of spring temperature limitation to plant productivity that results in earlier C uptake and a corresponding increase in magnitude of spring NEE from -19 to -144 gC m-2 season-1 by the end of the century. Although a similar relaxation of temperature limitation will occur in the fall, radiation limitation during those months will limit increases in C fixation. Additionally, warmer soil temperatures and increased carbon inputs from plants lead to combined fall and winter C losses (163 gC m-2) that are larger than summer net uptake (123 gC m-2 season-1) by year 2100. However, this increase in microbial activity leads to more rapid N cycling and increased plant N uptake during the fall and winter months that supports large increases in spring NPP. Due to the large increases in spring net C uptake, the high-latitude atmospheric C sink is projected to sustain throughout this century. Our analysis disentangles the effects of key environmental drivers of high-latitude seasonal C balances as climate changes over the 21st century.

Bias Correction, Historical Evaluations and Future Projections of Climate Simulations in the Wei River Basin Using CORDEX-EA

The utilization of Regional Climate Methods (RCMs) to predict future regional climate is an important study under the changing environment. The primary objective of the paper is to correct the temperature and precipitation simulations for the period of 1980-2005 and 2026-2098 in the Wei River Basin (WRB), to evaluate the performance of RCMs for the period of 1980-2005, and further, to analyze the future changes of projected temperature and precipitation during 2026-2098. In this paper, the linear scaling method was used to correct the temperature simulations. Quantile mapping, local intensity scaling method and hybrid method were used to correct the precipitation simulations. The future changes of projected temperature and precipitation for the near-term (2026-2050), mid-term (2051-2075) and far-term (2076-2098), relative to the period of 1980-2005, were investigated under RCP 2.6 and RCP 8.5. Results indicate that: (1) The temperature biases were different spatial distributions, and the precipitation wet biases were detected in the WRB. After correction, HadGEM2-ES driven by RegCM4-4 had the best temperature reproducibility, and NCC-NorESM1-M driven by RegCM4-4 had the best precipitation reproducibility. (2) Under RCP 2.6, the projected annual, winter and spring temperature showed decreasing trends. The temperature was higher than that for the period of 1980-2005 except for the spring temperature decreases in the Beiluo River Basin. Under RCP 8.5, the temperature showed significantly increasing trends. The temperature for the near-term was similar to the period of 1980-2005, while the temperature increased significantly for the mid-term and far-term. (3) Under RCP 2.6, the precipitation had decreasing trends. Under RCP 8.5, precipitation trends were also spatially distributed. The relative deviation of winter precipitation was the largest. Relative to the period of 1980-2005, the light and moderate rain days showed little change for the period of 2026-2098, while the extreme rain days showed significantly increasing trends. (4) The results could be beneficial to the future climate projection, which provide references for the water resources management, the future hydrological process changes and attribution analysis in the WRB.

Research On the Multiscale Characteristics of the Early Spring Temperature and Response To Climate Indices Over the Past 179 Years in the Qinling Mountains

Examination of the periodic differences in temperature in the Qinling Mountains at different time scales is highly important in research on the long-term evolution of the regional climate system and ecological environment. Based on February-April temperature data from 1835 to 2013 obtained at 27 weather stations in the Qinling Mountains reconstructed through tree rings, the multiscale characteristics of the early spring temperature time series on the southern and northern slopes of the Qinling Mountains and the response to climate signals were analyzed. The results indicate that the early spring temperature in the Qinling Mountains exhibits significant periodic characteristics on multiple time scales. Reconstruction at the different time scales reveals that the interannual scale change in the temperature variation on the northern slope of the Qinling Mountains plays a decisive role. The temperature on the northern slope exhibits a higher amplitude at the interannual and interdecadal scales than does that on the southern slope, and temporal differences occur at the quasi-century scale. The temperature achieves the strongest correlation with the original Atlantic Multidecadal Oscillation (AMO) sequence during the entire study period. In addition, the different time scales reveal that there exists a significant response relationship between the temperature at the interannual scale and the May sea temperature in the NINO3.4 area, which lags by one year. At the different time scales and various time ranges, the Qinling early spring temperature responds differently to the climate signals, which is an important factor leading to a lower correlation during the entire study period.

Differential response of distinct copepod life history types to spring environmental forcing in Rivers Inlet, British Columbia, Canada

The temporal dynamics of five copepod species common to coastal waters of the Pacific Northwest were examined in relation to variability in spring temperature and phytoplankton dynamics in 2008, 2009, and 2010 in Rivers Inlet, British Columbia, Canada. The five species were differentiated by life history strategies. Acartia longiremis, Metridia pacifica, and Paraeuchaeta elongata remained active over most of the year. By contrast, the reproductive effort of Eucalanus bungii and Calanus marshallae was concentrated over the spring period and they spent most of the year in diapause as C5 copepodites. A delay in the timing of the spring bloom was associated with a shift in the phenology of all species. However, following the delay in spring bloom timing, recruitment to the G1 cohort was reduced only for E. bungii and C. marshallae. Recruitment successes of E. bungii and C. marshallae was also drastically reduced in 2010, an El Niño year, when spring temperatures were highest. Reasons for the observed differential response to spring environmental forcing, and its effect on upper trophic levels, are discussed.

Modeling phenological reaction norms over an elevational gradient reveals contrasting strategies of Dusky Flycatchers and Mountain Chickadees in response to early-season temperatures

We developed an approach to distinguish among 3 alternative strategies that birds may employ relating the timing of egg laying across elevations to annual variation in spring temperature (phenological reaction norms), which we applied to analyze the breeding phenology of 2 species over an elevational gradient in the Sierra Nevada, California. In a “simple-offset” strategy, birds at different elevations initiate breeding relative to environmental temperature in a consistent manner, in that breeding onset is triggered by a critical temperature regardless of when it occurs in the spring. Elevation-specific reaction norms based on multiple years are offset (high-elevation birds start breeding later) but parallel. In a “delay” strategy, in cooler springs, populations at higher elevations that are sensitive to early-season weather-related risks delay laying onset relative to those at lower elevations, yielding a high-elevation reaction norm that diverges from a low-elevation one at cooler temperatures. Conversely, high-elevation populations in cooler springs that are sensitive to the risk of having insufficient time to complete a breeding cycle advance laying onset relative to lower populations (“advance” strategy), yielding a high-elevation reaction norm than converges with a low-elevation one. Both delay and advance strategies imply an elevation-dependent interaction between temperature and date (photoperiod) in influencing laying onset. Examined across 3 elevation groupings, phenological reaction norms of Mountain Chickadees (Poecile gambeli) were essentially parallel, consistent with simple offset, whereas Dusky Flycatchers (Empidonax oberholseri) relationships were more complex. In cooler springs, mid-elevation flycatchers bred comparatively late relative to lowest-elevation birds (delay), implying greater sensitivity to early-season risks, but still with sufficient time to complete a breeding cycle. However, high-elevation flycatchers bred comparatively early relative to mid-elevation populations (advance); delaying at these highest elevations may not be an option. Our approach revealed differences in risk sensitivity that were consistent with other ecological differences between the 2 species.

Improving the Spring Air Temperature Forecast Skills of BCC_CSM1.1 (m) by Spatial Disaggregation and Bias Correction: Importance of Trend Correction

In this study, an improved method named spatial disaggregation and detrended bias correction (SDDBC) based on spatial disaggregation and bias correction (SDBC) combined with trend correction was proposed. Using data from meteorological stations over China from 1991 to 2020 and the seasonal hindcast data from the Beijing Climate Center Climate System Model (BCC_CSM1.1 (m)), the performances of the model, SDBC, and SDDBC in spring temperature forecasts were evaluated. The results showed that the observed spring temperature exhibits a significant increasing trend in most of China, but the warming trend simulated by the model was obviously smaller. SDBC performed poorly in temperature trend correction. With SDDBC, the model’s deviation in temperature trend was corrected, and consequently, the temporal correlation between the model’s simulation and the observation as well as the forecasting skill on the phase of temperature were improved, thus improving the MSSS and the ACC. From the perspective of probabilistic prediction, the relative operating characteristic skill score (ROCSS) and the Brier skill score (BSS) of the SDDBC for three categorical forecasts were higher than those of the model and SDBC. The SDDBC’s BSS increased as the effect of the increasing resolution component was greater than that of the decreasing reliability component. Therefore, it is necessary to correct the predicted temperature trend in post-processing for the output of numerical prediction models.

Temperature Changes and Their Impact on Drought Conditions in Winter and Spring in the Vistula Basin

Inter-annual variability of hydro-meteorological variables indirectly influence soil moisture conditions in winter and early spring seasons. The interactions between temperature changes and drought conditions are studied by an application of statistical analyses of minimum temperature (Tmin), consecutive days with temperature exceeding the 0 °C threshold value, the number of melting pulses in the winter season and Standardized Evaporation Precipitation Index (SPEI). Additionally, shifts in the onset of days with spring temperature and snow cover occurrence are analysed. A Mann–Kendall test is applied for the trend analysis. Studies have shown significant changes in thermal characteristics in the winter season over the past 70 years, which affect the moisture conditions in the Vistula River Basin. As a result of those changes, the Vistula Basin is more prone to droughts.